Incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of boxers

OBJECTIVE: To determine incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of Boxers. ANIMALS: 1733 Boxers from 325 litters. PROCEDURE: Status of Boxers with respect to clinical signs of canine hip dysplasia (cCHD) was registered during an 8-year period. Survival analysis accounted for dogs lost to follow-up. Effective heritability for developing cCHD was estimated by use of a proportional hazard model on the basis of the Weibull distribution. Parametric survival models were developed to identify the influence of potential risk factors. RESULTS: Cumulative hazard rate for cCHD from 7 weeks to 8 years of age was 8.5%. Dogs that were kept on a floor covered with a slippery material were 1.6 times as likely to develop cCHD, compared with dogs kept on a nonslippery floor. Risk of cCHD doubled in dogs from litters with a high preweaning mortality rate. Dogs that were neutered at 6 months prior to a diagnosis of CHD were 1.5 times as likely to develop cCHD, compared with sexually intact dogs. Dogs >5 years of age were 1.8 times as likely to develop cCHD, compared with younger dogs. Estimated effective heritability of cCHD was 0.11. In terms of the risk of cCHD in progeny, mean estimated breeding value (EBV) of the 10 best and 10 worst sires was -0.32 and 0.42, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Registration of Boxers that develop cCHD may provide a strategy for disease prevention. In addition to diagnostic evaluation of radiographs, sire EBVs provide useful information for breeding selection decisions.